Question of flash metering

[J.A.F. Doorhof]

Believe it or not but today I got my first flash meter, the Sekonic L358.

I will be playing arround with it this week, but after reading the manual I would like some answers from the experienced guys over here to see if I have understand it correctly.

1. in the studio
If I want a face lit very evenly I disconnect all flashes except one and measure it from the face of the model it is lighting. After that I measure the second flash solo these two settings must be equal.

Seems fairly simple.
But what happens on the area's were the 2 flashes overlap ?
Can we measure this with both flashes operative ?
And take for example 3 measurements, one left, middle right ?

2. Outside.
This REALLY puzzles me.
If I want to use flash outside and get the real glam look (hard flash in).
I THINK I have to set the L358 to ambiant measuring and make a reading of a danger area (for example the hair), take for example f 11 @ 250 (Is it true I can never get above the 250 because of flash sync problems ??)
Now I change to flashcord setup and set the shutterspeed to 250 and take a measurement on the model and do this untill my flash output is f13. Now set the camera to 250 f13 and take the shot.
If I'm thinking right the model will not be blown out by the natural light (being under f13 and the flash will be harsch.

There is also another setting called flash percentage where the ambiant light is measured with the flash output.
Is it not better to use this setting and set the shutter for 250 and take the reading for example 70% flash for very hard flash and darker backgrounds and for example 50% for a more fill in flash.

3. Shutter speed
Last question, allready asked in 2 :D
Can I set a shutterspeed higher than 250 when using studio strobes ?
When doing in the studio I get very dark pictures and strange artifacts, when lowering to arround 250 it's perfect.
HOWEVER when using the 580EX I can get perfect fill in flash with 1/1000's but the 580EX has a HS flash setting which my studio strobe does not have.

Sorry for all the questions, but maybe someone has a clear answer.

Thanks in advance.

Greetings,
Frank

[scottbergerphoto]

The Sekonic L358 will tell you the relative contribution of ambient and flash light on the display in flash metering. You will need to take a separate ambient reading. You can't use a shutter speed faster then the sync speed or only part of the frame will be illuminated. I suggest that you use your Shutter Speed to handle the ambient light (below max sync speed), and the aperture to handle the flash output. Scott Smith of www.lightingmagic.com , reccommends always leaving all your lights on when flash metering. He takes readings by changing his position relative to the lights. I highly reccommend his book, available on his web site.

[chtgrubbs]

1. Where the coverage of two flashes overlap the light is additive and you will have one f-stop more light. If you are using broad soft sources like umbrellas or boxes it probably won't be too noticeable. If you are using harder sources you can feather the light to help overcome the difference.

2. You are correct here. Your flash will be 1/2 stop brighter than the ambient light and give you the hard look you want.

3. Shutter speed in the studio isn't very important unless you have a very bright modelling lights or a high ambient light level. The strobe is usually so much brighter and of such short duration that ambient light levels won't register. The high speed synch is only really necessary when using flash outdoors for fill or when used in your example above.

[J.A.F. Doorhof]

Ok thanks.
I have been playing arround a bit today and made some findouts, please tell me if they are correct.

When measuring a white background, I place the L358 for the background (1-2 cm) with the dome down, than I take the reading from that location.
This is the exact point where there is no blow out, just add 1 stop more for blow out.

I tried it on 4 different way's.

1.
Measured from the location of the camera pointing to the background, false reading gave 4.8 while it should have been f 11.00

2.
Measured with outward dome before the paper, gave f8.00 false

3.
Measured with outward dome pointed at the paper (15-20 cm's away) also gave f8.00 false

4.
Measured with extracted (inward dome) pointed to the flash 1-2 cm's from the paper giving arround f11.0

So that should be the correct way ??
Also tried this on a white T-shirt of my wife, measured with the dome out gave PERFECT reading for her face, but blew out the white T-shirt, when measuring with inward dome it gave f13.00 which was PERFECT for the shirt, exposed to the right at maximum.

@Scott I will order that book right away.

[scottbergerphoto]

If you are taking readings from the camera position, that is a reflected light reading. Flash requires incident metering at the location where you want the reading and pointed towards the camera eg. subjects face, in front of the background, etc. The dome should be out unless you are trying to measure a single light source.

[J.A.F. Doorhof]

Ok I understand that.
But when I measure with the dome out on my white background I get way too low readings, meaning I will blow out the backdrop from f8.00 measured to f13 what it should be.
Same on the white t-shirt, when I drop the dome in and measure white it gives the perfect reading.

When measuring the face by the normal way (dome out) it goes perfect.

[scottbergerphoto]

I have no explanation for why the dome out gives you f/8 and the dome in f/13. I would understand if it was the reverse as the dome out would be seeing your fill lights.

[J.A.F. Doorhof]

I was testing with just one flash on a white seamless paper background.

When I look in the manual it does make sense a bit.
The inward dome should be used for papers and paintings, the outward dome for everything 3 Dimensional like buildings and people.

I will be testing some more tomorrow in real live situations with a model.

[scottbergerphoto]

I was testing with just one flash on a white seamless paper background.

When I look in the manual it does make sense a bit.
The inward dome should be used for papers and paintings, the outward dome for everything 3 Dimensional like buildings and people.

I will be testing some more tomorrow in real live situations with a model.
It's an incident reading, so the kind of surface should affect the resulting picture or a reflected reading, not the incident reading.

[J.A.F. Doorhof]

correct, that's what puzzling me.
I have focused on dot on my white backdrop and wanted it to blow out just barely.
With the normal readings I got way overblown backgrounds.

Could it be that the backdrop (paper) reflects more than it gets (has white paper a gain value ??)

I will test more today maybe it will figure itself out today :D.

[PhotosGuy]

Frank, if I were doing it, I'd take an overall reading & then look at the pic to see what the result is. Digital makes things SO much easier than the film "shoot & pray" metered approach!
No model yet? No problem! Use the self timer & take a shot of "self"! ;-)

[J.A.F. Doorhof]

Hi,
I had the same opinion but too often I ran into problems with multiflash setups and just blown out area's and balance problems on faces.

Today I had the first session with the meter and it's PERFECT.
I can now get beautiful evenly lit faces from 2 different flashes, which I normaly never could get perfect, I could do it for 90% but never the full 100% perfect.

I will never work without the meter again :D

[PhotosGuy]

Different strokes... ;-)

[J.A.F. Doorhof]

Tried it and you like it :D

Do you have a light meter ?

[Henry Low]

when you guys are talking about flashes, are u talking about Hot shoe flashes such as teh Canon EX and the Sigma supers?

I am planning to get a light meter too... and also been puzzled at the fact at how it will meter multiple wireless flashes together. :(

Seems very complicated trying to render in my mind how it would work without getting blown on faces. Someone explain to me how you guys normally do it say if u had 3 flashes on a model, how would u use a light meter to get the right exposer of all 3 flashes?

[PhotosGuy]

Do you have a light meter ?
Several, including strobe. I used/liked/needed them when I shot film. Now they gather dust. A histogram covering the important pic area does it for me now & the LCD gives me enough eyeball info before RAW processing. OTOH, if a client showed up with a P&S, I might dig out the meter & wave it around just to assert my "Professionalism" & keep him in his place! :D:D:D

[J.A.F. Doorhof]

@photos,
I agree on some points, the histogram is superb for evaluating.
But often I want rather large contrasts on my pictures for example a strong rim light and a barely visable front, I can use my LCD for that but it takes me arround 20-30 shots to get it as I want, while with the meter I can set the rims at f11 and the front at f5.6 and get exactly what I want.

Also I find it imposible to eyeball a perfect lit face on the LCD one side is alway's a bit darker or lighter than the other.

Also the white backgrounds are often TOO much overblown, meaning I will loose defenition in the hairs, when I meter it to f11 and the front to f8.00 I can see even the smallest hairs on the model and get a bright white background.

@Henry,
Measuring hotshoe flash is something I leave to my E-TTLII.
I use the meter for my studio strobes.
I start out with my keylight (brightest) and after that I get more and more flashes in the shot.

[Henry Low]

can wireless slaves be leaved on E-TTLII? including sigma super 500 dgs?

thanks,
henry

@photos,
I agree on some points, the histogram is superb for evaluating.
But often I want rather large contrasts on my pictures for example a strong rim light and a barely visable front, I can use my LCD for that but it takes me arround 20-30 shots to get it as I want, while with the meter I can set the rims at f11 and the front at f5.6 and get exactly what I want.

Also I find it imposible to eyeball a perfect lit face on the LCD one side is alway's a bit darker or lighter than the other.

Also the white backgrounds are often TOO much overblown, meaning I will loose defenition in the hairs, when I meter it to f11 and the front to f8.00 I can see even the smallest hairs on the model and get a bright white background.

@Henry,
Measuring hotshoe flash is something I leave to my E-TTLII.
I use the meter for my studio strobes.
I start out with my keylight (brightest) and after that I get more and more flashes in the shot.

[J.A.F. Doorhof]

Depends, I have a 580EX and a 420EX which I sometimes use for shoots outside and Ettl works fine, never have to worry to be honest.

Recently I bought a portable studio flash head and that will have to be metered.

[Henry Low]

Depends, I have a 580EX and a 420EX which I sometimes use for shoots outside and Ettl works fine, never have to worry to be honest.

Recently I bought a portable studio flash head and that will have to be metered.


Whats the advantages of usiong studio flash head?

Thanks for your help JAF

[J.A.F. Doorhof]

1.
More powerful
2.
Better use of lightmodifiers like softboxes, grids etc.
3.
You can get EXACTLY what you want fairly easy.

[SkipD]

when you guys are talking about flashes, are u talking about Hot shoe flashes such as teh Canon EX and the Sigma supers?

I am planning to get a light meter too... and also been puzzled at the fact at how it will meter multiple wireless flashes together. :(

Seems very complicated trying to render in my mind how it would work without getting blown on faces. Someone explain to me how you guys normally do it say if u had 3 flashes on a model, how would u use a light meter to get the right exposer of all 3 flashes?Henry - after looking at your several posts, it is obvious to me that you need to understand something about flash systems. If you are using a flash system that is CONTROLLED by the camera - TTL, ETTL or variations of them - there is absolutely nothing that a handheld light (flash) meter will do for you.

With ETTL, or any of the variations, the combination of camera and automatic flash unit(s) (which communicate together as a system) controls the exposure and there is little you can do about the results except to use Flash Exposure Compensation.

When you eliminate the automatic flash units (typical hotshoe flash systems) and use an off-camera flash that is only TRIGGERED by the camera and not controlled by the camera, you set the camera into a manual mode. Here is where a flash meter comes in handy. The meter will measure the intensity of the light from the flash unit(s) and show you how to set the f-stop for the lighting setup.

If you try to trigger an off-camera flash system (one which does not communicate with the camera, such as a studio flash unit) with an on-camera flash (either built in or hotshoe type), you will seldom get good results. The reason is that the camera and the on-camera flash communicate together and attempt to control the exposure. The camera cannot communicate with, for example, a studio flash. Thus, the exposure will likely be very different from what you desire.

[scottbergerphoto]

Basic facts:

Dome retracted: reflective mode

Dome out: incident mode

The dome has an averaging effect when it is extended.

The dome does not average when it is retracted. The light striking the tip of the dome is what the sensor below the dome reads.

Some meters provide a flat panel to place over the sensor when you want to take a reflective reading.

When using flash ALWAYS take incident readings. To determine ratios, point the dome toward the light. To get an average readin the face,take areading from the face with the dome pointing toward the camera. To determine ratios of lighting on the face, point it toward the light source.

You will ALWAYS get different readings in reflective and incident mode.
Not exactly correct. If you want an incident reading of single strobe you use the dome retracted. The dome isn't designed for reflected readings at all. You have to remove the dome completely and use a separate attachment with a small clear glass sensor. It is clearly explained in the instructions for the L358.
Notice the list of items included with the L358 and you will see something called "Reflected Light Attachment".
http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=221078&is=REG&addedTroughType=search

[iwatkins]

I've come to this one late Frank, so bear with me.

I use the 358 in the studio and have done from day one (I salute you for your shots even more now I see you haven't been using a meter).

For main/fill lights, I measure with the dome out and the dome pointing at the camera (or where the camera will be). If there is a big difference in power to my main and fill I'll meter them both individually. However, if the lighting is to be fairly flat I'll meter them both at the same time. I'll just meter all around the head and upper body to ensure light falloff isn't too large.

For a pure white background, the model is usually a long way from the paper/vinyl. I'll meter the background light(s) on their own (main and fill off). I'll use the 358 with the dome retracted and pointed at the part of the paper where the models head will align. The meters retracted dome will be pointed at the paper *not* the camera. I'll do this from about 1 metre away. I'll also meter several positions around the paper to ensure falloff isn't so great that'll I'll end up with pure white and a bit of grey. I'll keep doing this until my background is 2 stops brighter than my main/fill combination. Anymore than 2 stops and we are into hair disappearing and light bleed around the arms etc.

Cheers

Ian

[SkipD]

The 54 degree Lumigrid does (essentially) what retracting the dome does: it narrows the the angle of light that hits the dome.(Look at how the 308 achieves a reflective reading by sliding the dome). Outdoors, you can do the same thing by cupping your hand around the top of the dome. As long as you aren't standing on a beach or a highly light reflective surface, you'll get a reflective reading.I just tested my L-358 measuring reflected light with the Lumigrid and with the dome installed but retracted. There is a 3-stop difference in the readings, as I suspected there would be.

In addition, the Lumigrid focusses light via a fresnel lens in order to measure the average across a controlled 54-degree receiving angle. The dome, even when retracted, can be illuminated by light sources far outside the 54-degree angle.

You can not use the dome for conventional reflected readings unless you compensate by the three stops, and I suspect even then it wouldn't give the quality of results (selectivity of the target) that the Lumigrid does for reflected readings.

I just checked the Sekonic website and looked at a manual for the 308. It is like an ancient meter I own. The dome is merely moved out of the way of a lens that takes in light for reflective readings or is moved to cover the lens to make incident readings.

[SkipD]

Three stops?

How are you using your light meter, and how long have you been using a light meter?I've been using light meters for about 40 years now. Of course, my L-358 wasn't invented when I started using meters. My test was measuring the light falling on a wall in the house. It was fairly evenly lit. I was using the meter as a reflective meter - aiming the sensor at the wall - in both cases.

I just went outdoors and took several readings. The first reading was an incident reading with the dome on and pointed directly up at a cloudy sky. The second was a reflected reading with the Lumigrid on, and pointed directly down at our medium grey patio which was lit by the sky with no shadows. The third was with the dome on, but pointed at the patio in a reflected reading mode. The third reading was three stops lower than the reflected reading with the Lumigrid mounted - the same as my interior wall test.

When you think about it, the sensor in the meter (with no adapter plugged in) is just "looking" at light. With the Lumigrid, it is looking through a fresnel lens with very little loss. With the dome mounted, it is looking at the light that gets through to the interior surface of the dome.

Try this test. Hold your dome up to the sky at arm's length and look into its interior as if you are the meter. You will see that the inside of the dome is a lot darker than the surrounding sky. Now hold the Lumigrid up to the sky the same way. Except for the lens effect, the image of the sky will be as bright as the surrounding sky.

The reason for this testing was that folks were saying that you could meter reflected light with the dome mounted. This, without some serious compensation, is not true.

[J.A.F. Doorhof]

Have been trying more today and using the meter with dome extended will work perfect for me.
Also for the white backgrounds by the way, I don't know why the first test went wrong, but now I can recreate perfect readings every time.

And more creativity :D

New shoot done today and we did some shots which were impossible to eyeball, will be posting some new stuff (and a movie) this weekend.

[Todd Jacobsen]

Henry - after looking at your several posts, it is obvious to me that you need to understand something about flash systems. If you are using a flash system that is CONTROLLED by the camera - TTL, ETTL or variations of them - there is absolutely nothing that a handheld light (flash) meter will do for you.



Not quite true. The light meter will give you a rough estimate of the incident light at subject. That rough estimate, even with ETTL, will be pretty close.

ETTL evaluates the amount of ligh required for EVERY shot. That does not mean EVERY shot will have a different flash amount. It just means you cannot guarantee that same amount will ALWAYS be there. ETTL will not vary wildly, but differences can be (not necessarily will be) discernible - if a shot-to-shot comparison is conducted for pictures whos environment (setting) never changed.

A wedding album MAY show these variances, but with difference poses, people, and settings, these frequent "re-calculations" are not noticed as much. They will become apparent based on subject dress (colors).

The only problem with utilizing the lightmeter (particularly L358 ) with ETTL, is inhibiting (if you can) the lightmeter reading the pre-flash.

[scottbergerphoto]

Why would you use a Flashmeter with ETTL other then to asess the actual ratios the system is giving you with multiple flash(or ambient light)? You cannot use it to adjust flash output as the ETTL will just override any adjustment you make to f stop or shutter speed to give what it thinks is the correct exposure.

[SkipD]

Why would you use a Flashmeter with ETTL other then to asess the actual ratios the system is giving you with multiple flash(or ambient light)? You cannot use it to adjust flash output as the ETTL will just override any adjustment you make to f stop or shutter speed to give what it thinks is the correct exposure.I couldn't have stated that any better, Scott. Thanks.